JP2009258434A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device excellent in workability in which urging members used to urge a lever member are fitted to the device, and to provide an image forming apparatus. <P>SOLUTION: The fixing device includes pressure reducing means 64 and 66 for putting a pressure member 30 and a fixing member 20 in a pressure reduction state by moving the support point part 61a of a lever member 61 away from the pressure member 30. The urging member 62 and 63 for urging the lever member 61 at a power point part 61b are fitted to the device so as to urge the lever member 61 while the pressure member 30 and fixing member 20 are put in the pressure reduction state by the pressure reducing means 64 and 66. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein, and in particular, a recording medium in which a fixing member and a pressure member are pressed. The present invention relates to a fixing device and an image forming apparatus that form a nip portion where the toner is conveyed.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, a fixing device that performs a fixing process while forming a nip portion by pressing a fixing member and a pressure member and conveying a recording medium to the nip portion. Is widely known (see, for example, Patent Documents 1 to 3).

  In Patent Document 1, etc., the pressurizing mechanism of the fixing device includes a pressurizing arm (lever member) installed to be rotatable about a fulcrum shaft, a compression spring (biasing member) that biases the pressurizing arm, and the like. It consists of The pressurizing arm engages with the pressurizing member and pushes the pressurizing member toward the fixing member with the point of action between the fulcrum shaft and the position (power point) urged by the compression spring. The member is in a pressurized state.

  In Patent Document 2, etc., the pressure mechanism of the fixing device includes a pressure lever (lever member) installed to be rotatable around a fulcrum shaft, a tension spring (biasing member) that urges the pressure lever, and the like. It consists of The pressure lever engages with the pressure member and pushes the pressure member toward the fixing member with the point between the fulcrum shaft and the position (force point) urged by the tension spring as an action point. The member is in a pressurized state.

  On the other hand, Patent Document 3 discloses a technique for switching a fixing member and a pressure member in a pressurized state to a reduced pressure state. Specifically, the pressure mechanism of the fixing device includes a pressure lever (lever member) installed to be rotatable about a fulcrum shaft, a cam that contacts one end of the pressure lever, and the like. The pressure lever engages with the pressure member and pushes the pressure member upward toward the fixing member with the point of action between the fulcrum shaft and the position (power point) where the cam comes into contact, and adds both members. It is in a pressure state. Then, by rotating the cam by a predetermined angle, the contact position with the pressure lever is moved downward, so that the fixing member and the pressure member are in a reduced pressure state.

JP 2007-79160 A Japanese Patent Laid-Open No. 10-282828 JP 2008-40010 A

The above-described conventional fixing device has poor workability for assembling an urging member such as a compression spring or a tension spring for urging the lever member during manufacture or maintenance.
Specifically, when the spring is assembled to the fixing device, a large force is applied to the spring connected to one end of the lever member so that the spring length is largely changed from the free length to the frame of the fixing device. Had to connect. That is, it is necessary to apply a large force when the urging member for urging the lever member is assembled to the fixing device. Similarly, when removing the biasing member from the fixing device, for example, during maintenance, it is necessary to apply a large force.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a fixing device and an image forming apparatus that have good workability when assembling a biasing member that biases a lever member. .

  According to a first aspect of the present invention, a fixing device includes a fixing member that heats and melts a toner image and fixes the toner image on a recording medium, and a nip portion that is pressurized by the fixing member and transports the recording medium. A pressure member to be formed and an action point portion between the force point portion and the fulcrum portion that are installed so as to be rotatable about the fulcrum portion and are urged by an urging member installed at the force point portion. A lever member that engages the pressure member or the fixing member to bring the pressure member and the fixing member into a pressurized state, and the fulcrum portion of the lever member is the pressure member or the fixing member. And a pressure reducing unit that moves the pressure member and the fixing member to a pressure-reduced state by moving the pressure member and the fixing member away from each other, and the biasing member reduces the pressure member and the fixing member in a pressure-reduced state by the pressure reducing unit. The lever member is energized while maintaining Those assembled to device.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the biasing member includes a tension spring whose one end is connected to the force point portion of the lever member, and the tension spring. And a second lever member configured to be rotatable about a support shaft. The support shaft of the second lever member includes the second lever member connected to the other end of the second lever member. 2 is arranged at a position where the distance between the force point portion and the hook portion is variable in conjunction with the rotation of the lever member, and the urging member depressurizes the pressure member and the fixing member by the pressure reducing means. The second lever member is rotated around the support shaft while maintaining the state, and is assembled to the apparatus so as to urge the lever member by the spring force of the tension spring.

  The fixing device according to a third aspect of the present invention is the fixing device according to the second aspect, wherein the pressure reducing means rotates the second lever member around the support shaft and uses the tension spring. The pressure member and the fixing member are changed from a first reduced pressure state to a second reduced pressure state before and after the lever member is urged by a spring force.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the pressure reducing means regulates a direction in which the fulcrum portion of the lever member moves. A regulating member and an engaging member that engages with the lever member are provided.

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect of the present invention, the engagement member is a cam member, and the cam member is rotated and driven by a drive unit. The orientation of the direction is maintained and the pressure member and the fixing member are switched from the reduced pressure state to the pressurized state.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to the fifth aspect, wherein the cam member adds the pressure member and the fixing member when the driving unit is not operating. The pressure member and the fixing member are rotated so as to be in a reduced pressure state by pressure.

  The fixing device according to a seventh aspect of the present invention is the fixing device according to the fourth aspect, wherein the engaging member is a protrusion provided on a cover of the main body of the image forming apparatus. When the cover of the image forming apparatus main body is closed, the pressure member and the fixing member are brought into a pressurized state by engaging with the lever member, and the cover of the image forming apparatus main body is opened. The engagement with the lever member is released when the pressure member and the fixing member are in a reduced pressure state.

  The fixing device according to an eighth aspect of the present invention is the fixing device according to the fourth aspect, wherein the engaging member is a protrusion provided on a main body of the image forming apparatus. When the apparatus is mounted on the image forming apparatus main body, the pressure member and the fixing member are brought into a pressurized state by engaging with the lever member, and the apparatus is taken out from the image forming apparatus main body. The engagement with the lever member is released to bring the pressure member and the fixing member into a reduced pressure state.

  An image forming apparatus according to a ninth aspect of the present invention includes the fixing device according to any one of the first to eighth aspects.

  In the present application, the “depressurized state” between the pressure member and the fixing member is a pressurized state (a state in which a normal fixing process is performed by forming a nip portion, and no decompression is performed by the decompression means. It is defined as a state other than a state) that indicates a state in which the pressure between the pressure member and the fixing member is smaller than that in the pressure state. Therefore, even when the pressure between the pressure member and the fixing member is reduced in stages (when the states of different pressure reduction are formed in stages), each stage is a “depressurized state”. It will be.

  In the present invention, the urging member is assembled to the fixing device such that the fulcrum portion configured to be movable is moved to urge the lever member while maintaining the pressure member and the fixing member in a reduced pressure state. Accordingly, it is possible to provide a fixing device and an image forming apparatus that have good workability when the urging member that urges the lever member is assembled.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is the main body of a tandem type color copier as an image forming apparatus, 2 is a writing unit that emits laser light based on input image information, 4 is a document reading unit that reads image information of a document D, and 7 is A paper supply unit for storing a recording medium P such as transfer paper, 11Y, 11M, 11C, and 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, and 12 is a photosensitive drum. 11Y, 11M, 11C, and 11BK are charged. 13 is a developing unit that develops an electrostatic latent image formed on each photoconductor drum 11Y, 11M, 11C, and 11BK, and 15 is each photoconductor drum 11Y. A cleaning unit that collects untransferred toner on 11M, 11C, and 11BK is shown.
Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred, and 18 a color image formed on the intermediate transfer belt 17 as a recording medium. A secondary transfer roller 19 for transferring the toner image onto P is an electromagnetic induction heating type fixing device for fixing a toner image (unfixed image) on the recording medium P.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, image information of the document D placed on the contact glass 5 is optically read by the document reading unit 4. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.
Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotational axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y after being charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated to the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller (not shown) is installed at each facing portion so as to abut on the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photoconductive drums 11Y, 11M, 11C, and 11BK are sequentially transferred to the intermediate transfer belt 17 at the position of the transfer bias roller (primary transfer process). .)

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the primary transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

Thereafter, the intermediate transfer belt 17 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 18. At this position, the secondary transfer backup roller sandwiches the intermediate transfer belt 17 between the secondary transfer roller 18 and forms a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 17 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip (secondary transfer process). At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 17.
Thereafter, the intermediate transfer belt 17 reaches the position of the intermediate transfer cleaning unit 16. At this position, the untransferred toner on the intermediate transfer belt 17 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 17 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip passes through a transport path K1 in which a paper feed roller 8, a registration roller, and the like are installed from a paper feed unit 7 disposed below the apparatus main body 1. It was transported via.
Specifically, a plurality of recording media P are stored in the paper supply unit 7 in a stacked manner. When the paper feed roller 8 is rotationally driven counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the transport path K1.

  The recording medium P transported to the transport path K1 temporarily stops at the position of the roller nip of the registration roller (not shown) that has stopped rotating. Then, the registration roller is driven to rotate in synchronization with the color image on the intermediate transfer belt 17, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 19. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
The recording medium P after the fixing process is discharged as an output image by the paper discharge roller 9 to the outside of the apparatus main body 1 (moving in the direction indicated by the broken line arrow), and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 19 installed in the image forming apparatus main body 1 will be described in detail.
As shown in FIG. 2, the fixing device 19 includes an induction heating unit 25 (magnetic flux generating means), a fixing roller 20 as a fixing member facing the induction heating unit 25, and a pressure as a pressure member that presses against the fixing roller 20. It comprises a roller 30, an inlet guide plate 41, a spur 42, a separation plate 43, a guide member 50, and the like.

Here, the fixing roller 20 as a fixing member is formed by sequentially laminating a heat insulating elastic layer 22 made of foamed silicone rubber or the like and a sleeve layer 21 on a cored bar 23 made of iron or stainless steel, The outer diameter is about 40 mm.
The sleeve layer 21 of the fixing roller 20 is a multilayer structure in which a base material layer, a first antioxidant layer, a heat generating layer, a second antioxidant layer, an elastic layer, and a release layer are sequentially laminated from the inner peripheral surface side. Specifically, the base material layer is formed of stainless steel having a layer thickness of about 40 μm, and the first antioxidant layer and the second antioxidant layer are formed by strike plating treatment of nickel having a layer thickness of 1 μm or less. The heating layer is made of copper having a layer thickness of about 10 μm, the elastic layer is made of silicone rubber having a layer thickness of about 150 μm, and the release layer has a layer thickness of about 30 μm. It is formed of PFA (tetrafluoroethylene / barfluoroalkyl vinyl ether copolymer).
In the fixing roller 20 configured as described above, the heat generating layer of the sleeve layer 21 is electromagnetically heated by the magnetic flux generated from the induction heating unit 25. The configuration of the fixing roller 20 is not limited to that of the first embodiment. For example, the sleeve layer 21 can be separated without being bonded to the heat insulating elastic layer 22 (fixing auxiliary roller). However, when the sleeve layer 21 (fixing sleeve) is separated, it is preferable to install a member for preventing the sleeve layer 21 from moving in the width direction (thrust direction) during operation.

Here, a plurality of spurs 42 are juxtaposed in the width direction at a position facing the fixing roller 20 and upstream of the nip portion (upstream in the transport direction). The spur 42 guides the recording medium P fed into the nip portion to the nip portion. The spur 42 is formed in a saw-tooth shape so that even if it contacts an unfixed image on the recording medium P, the image does not rub.
In addition, a separation plate 43 is installed at a position facing the fixing roller 20 and downstream of the nip portion (downstream in the transport direction). The separation plate 43 is for preventing a problem that the recording medium P after the fixing process sent out from the nip portion is attracted to and wound around the fixing roller 20. That is, when the recording medium P after the fixing process is attracted to the fixing roller 20, the separation member 43 interferes with the leading end of the recording medium P to forcibly separate the recording medium P from the fixing roller 20.
Although not shown, a thermopile (non-contact type temperature sensor) and a thermistor (contact type temperature sensor) are disposed around the fixing roller 20. The temperature on the fixing roller 20 (fixing temperature) is detected by a thermopile or a thermistor. And the amount of heating by the induction heating part 25 is adjusted based on the detection result by a thermopile or a thermistor.

Referring to FIG. 2, a pressure roller 30 as a pressure member is formed on a cylindrical member 32 made of aluminum, copper or the like, an elastic layer 31 made of silicone rubber or the like, a release layer made of PFA or the like (not shown). Is formed). The elastic layer 31 of the pressure roller 30 is formed to have a thickness of 1 to 5 mm. The release layer of the pressure roller 30 is formed so that the layer thickness is 20 to 50 μm. The pressure roller 30 is in pressure contact with the fixing roller 20. Then, the recording medium P is conveyed to a pressure contact portion (a nip portion) between the fixing roller 20 and the pressure roller 30.
In the first embodiment, a heater 33 such as a halogen heater is provided in the pressure roller 30 in order to increase the heating efficiency of the fixing roller 20. By supplying electric power to the heater 33, the pressure roller 30 is heated by the radiant heat of the heater 33, and the surface of the fixing roller 20 is heated via the pressure roller 30.

Here, an inlet guide plate 41 is installed at a position facing the pressure roller 30 and upstream of the nip portion. The inlet guide plate 41 guides the recording medium P fed into the nip portion to the nip portion.
A guide member 50 is installed at a position facing the pressure roller 30 and downstream of the nip portion (a position facing the non-fixing surface of the recording medium P fed from the nip portion). Yes. The guide member 50 is for guiding the recording medium P sent from the nip portion after the fixing process toward the conveyance path after the fixing process.
In addition, with reference to FIG. 3, a grip portion 70 is installed on the guide member 50. Then, an operator such as a user or a serviceman moves the main part of the fixing device 19 when the jam of the recording medium P occurs at the position of the fixing device 19 (this is a phenomenon in which the recording medium P being conveyed is clogged). The jammed paper is gripped in a state where the gripping portion 70 is gripped and the guide member 50 is rotated around the rotation shaft portion 50a (rotation in the direction of the arrow in FIG. 2) to expose the nip portion. It will be pulled out and removed.

The induction heating unit 25 includes a coil unit 26 (excitation coil), a core unit 27 (excitation coil core), a coil guide 28, and the like. The coil portion 26 is wound in the width direction (in the direction perpendicular to the paper surface of FIG. 2) by winding a litz wire bundled with thin wires on a coil guide 28 disposed so as to cover a part of the outer peripheral surface of the fixing roller 20. It is extended. The coil guide 28 is made of a resin material having high heat resistance and holds the coil portion 26 on the side facing the fixing roller 20. The core portion 27 is made of a ferromagnetic material such as ferrite (having a relative magnetic permeability of about 2500), and is used to form an efficient magnetic flux toward the heat generating layer of the fixing roller 20, and includes an arch core and a center core. It is composed of a side core and the like.
The induction heating unit 25 is configured to be separable from the main part of the fixing device 19. Then, the main part (the unit shown in FIG. 3) of the fixing device 19 is separated from the induction heating unit 25 and taken out from the image forming apparatus main body 1 with the cover 100 opened.

The fixing device 19 configured as described above operates as follows.
The fixing roller 20 is driven to rotate counterclockwise in FIG. 2 by a drive motor (not shown), and the pressure roller 30 is rotated clockwise accordingly. The sleeve layer 21 (heat generation layer) of the fixing roller 20 is heated by the magnetic flux generated from the induction heating unit 25 at a position facing the induction heating unit 25.

  Specifically, the oscillation circuit causes a high-frequency alternating current of 10 kHz to 1 MHz (preferably 20 kHz to 800 kHz) to flow from the coil unit 26 to a coil unit 26 from a power supply unit (not shown) whose frequency is variable. The magnetic field lines are formed so as to alternately switch in both directions toward the sleeve layer 21 of the fixing roller 20. By forming an alternating magnetic field in this manner, an eddy current is generated in the heat generating layer of the sleeve layer 21, and the heat generating layer generates Joule heat due to its electric resistance and is induction-heated. Thus, the sleeve layer 21 (fixing roller 20) is heated by induction heating of its own heat generation layer.

Thereafter, the surface of the fixing roller 20 heated by the induction heating unit 25 reaches a contact portion (nip portion) with the pressure roller 30. Then, the toner image T (toner) on the conveyed recording medium P is heated and melted.
Specifically, the recording medium P carrying the toner image T through the image forming process described above is sent between the fixing roller 20 and the pressure roller 30 while being guided by the entrance guide plate 41 (or the spur 42). (The movement in the transport direction of the arrow Y1.) The toner image T is fixed on the recording medium P by the heat received from the fixing roller 20 and the pressure received from the pressure roller 30, and the recording medium P is sent out between the fixing roller 20 and the pressure roller 30 ( This is the movement in the transport direction of the arrow Y2.)
The surface of the fixing roller 20 that has passed through the nip portion then reaches the position facing the induction heating unit 25 again.
Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

Hereinafter, the configuration and operation of the fixing device 19 that are characteristic of the first embodiment will be described in detail with reference to FIGS.
FIG. 4 is a side view showing the pressure mechanism of the fixing device, and FIG. 5 is a perspective view showing the pressure mechanism of the fixing device. FIG. 6 is a top view showing the vicinity of the hook shaft 67 (hook portion) to which the tension spring 63 is connected. FIG. 7 is a side view showing a pressure state of the fixing device, and FIG. 8 is a side view showing a pressure reduction state of the fixing device. FIG. 9 is a side view showing a state in which the urging members 62 and 63 are assembled to the fixing device. Further, FIG. 10 is a schematic view showing the operation of the tension spring 63 at the time of FIG.

  Referring to FIGS. 4 and 5, the fixing roller 20 and the pressure roller 30 are rotatably supported via bearings by two side plates 60 provided at both ends in the width direction, respectively. Here, a long hole is formed in the side plate 60 so that the bearing supporting the pressure roller 30 can move in a direction in which the bearing is in contact with or separated from the fixing roller 20. Although not shown, the two side plates 60 are screwed to a stay extending in the width direction, and the two side plates 60 and the stay constitute a frame of the fixing device 19.

  The two side plates 60 of the fixing device 19 are provided with a pressure mechanism that puts the fixing roller 20 and the pressure roller 30 into a pressurized state. The pressurizing mechanism includes a pressurizing lever 61 as a lever member, biasing members 62 and 63 installed on a power point shaft 61b as a power point portion of the pressure lever 61, and the like. The urging member includes a release lever 62 as a second lever member, a tension spring 63, and the like.

The pressure lever 61 as a lever member is installed so as to be rotatable around a fulcrum shaft 61a as a fulcrum portion. Then, it engages with the pressure roller 30 (the bearing inserted in the shaft portion of the pressure roller 30) at the action point portion between the force point shaft 61b (force point portion) and the fulcrum shaft 61a (fulcrum portion). As a result, the pressure roller 30 and the fixing roller 20 are in a pressurized state.
Note that the fulcrum shaft 61 a of the pressure lever 61 is not fixed to the side plate 60, but is configured to be movable in a direction in which the fulcrum shaft 61 a contacts and separates from the fixing roller 20. Specifically, a fulcrum shaft 61a is fixed to one end of the pressure lever 61, and the fulcrum shaft 61a is movably inserted into a long hole of a slide bearing 64 as a regulating member. A long hole is formed at the other end of the pressure lever 61, and a stopper shaft 61c fixed to the side plate 60 is movably inserted into the long hole.

  The release lever 62 as the second lever member is configured to be rotatable about a support shaft 62a fixed to the side plate 60 (see also FIG. 9). One end of the tension spring 63 is connected to a force point shaft 61 b fixed to the pressure lever 61, and the other end is connected to a hook shaft 67 as a hook portion of the release lever 62.

  Here, referring to FIG. 6, the hook shaft 67 is held without being screwed to the release lever 62. Specifically, a small-diameter portion is provided at one end (the lower side of FIG. 6) of the hook shaft 67, and this small-diameter portion is engaged with the hole portion of the release lever 62. The other end of the hook shaft 67 (the upper side in FIG. 6) is engaged with the hole of the release lever 62. Further, the release lever 62 is rotatably held at a position relatively close to the side plate 60 by the support shaft 62a. With such a configuration, even when the hook shaft 67 held free with respect to the release lever 62 moves downward in FIG. 6, the step between the small diameter portion and the large diameter portion of the hook shaft 67 is related to the release lever 62. In addition, even if the hook shaft 67 moves upward in FIG. 6, the end surface of the hook shaft 67 is engaged with the side plate 60 and the movement of the hook shaft 67 in the axial direction is restricted. As described above, in the first embodiment, since the hook shaft 67 is held without being screwed to the release lever 62, the number of parts of the urging members 62, 63, and 67 is reduced, and the hook member 67 is attached. The assembling property of the urging members 62, 63, 67 can be improved.

Here, in the fixing device 19 according to the first embodiment, the fulcrum shaft 61 a of the pressure lever 61 is moved to a position away from the pressure roller 30, so that the pressure roller 30 and the fixing roller 20 in a pressurized state are moved. There is provided a decompression means for bringing
The decompression means rotationally drives the slide bearing 64 as a restricting member that restricts the direction in which the fulcrum shaft 61a of the pressure lever 61 moves, the cam member 66 as an engaging member that engages with the pressure lever 61, and the cam member 66. The drive unit 90, 91, 97, etc.

  One end of the slide bearing 64 is rotatably supported by the side plate 60, and an elongated hole into which the fulcrum shaft 61a of the pressure lever 61 is inserted is formed at the other end. Referring to FIG. 5, cam member 66 is installed on transmission shaft portion 99 so as to rotate together with transmission shaft portion 99. Further, a driven gear 97 and a detection plate 95 are installed on one end side of the transmission shaft portion 99 so as to rotate together with the transmission shaft portion 99. Then, the rotational driving force by the drive motor 90 is transmitted to the driven gear 97 of the transmission shaft 99 via the gear train 91, and the transmission shaft 99 rotates together with the cam member 66, the driven gear 97, and the detected plate 95. become.

Here, the detected plate 95 is for detecting the posture of the cam member 66 in the rotation direction by the photo sensor 96.
Specifically, when the detection plate 95 is not between the light emitting element and the light receiving element of the photosensor 96, the cam member 66 is in a posture to push up the pressure lever 61, and the fixing roller 20, the pressure roller 30, Is detected as being in a pressurized state (the state of FIG. 7). On the other hand, when the detection plate 95 is between the light emitting element and the light receiving element of the photosensor 96, the cam member 66 is not in a posture to push up the pressure lever 61, and the fixing roller 20 and the pressure roller 30 is detected as being in a reduced pressure state (the state of FIG. 8).

As described above, the cam member 66 is rotationally driven by the drive units 90, 91, and 97, and the posture in the rotation direction is maintained, so that the pressure roller 30 and the fixing roller 20 are changed from the reduced pressure state to the pressurized state. Will switch.
Specifically, during the normal fixing process, the cam member 66 is rotationally driven and held in the posture shown in FIG. At this time, the cam member 66 pushes up the pressure lever 66 in the direction of the white arrow in FIG. 7, and the fulcrum shaft 61a of the pressure lever 61 also moves in the left direction in FIG. Thus, with the fulcrum shaft 61a as a fulcrum, the force point shaft 61b on which the spring force of the tension spring 63 acts as the force point, and the pressure roller 30 as the point of action between the fulcrum shaft 61a and the force point shaft 61b, The pressure roller 30 and the fixing roller 20 are in a pressure state.
On the other hand, when the fixing process is not performed (during the non-fixing process), the cam member 66 is rotationally driven and held in the posture shown in FIG. At this time, the pressure lever 61 moves in a direction in which the holding force by the cam member 66 is removed and the pressure is reduced by the pressure between the pressure roller 30 and the fixing roller 20 (FIG. 8 rightward movement). At this time, the fulcrum shaft 61a of the pressure lever 61 also moves to the right in FIG. Thus, the pressure roller 30 and the fixing roller 20 are in a reduced pressure state.

Note that the pressure roller 30 and the fixing roller 20 are in a reduced pressure state at the following timing.
First, during the non-fixing process, the rotational drive of the cam member 66 is controlled so that the pressure is reduced. In addition, in order to provide a margin during the fixing process that is in a pressurized state, the recording medium P is in a pressurized state for a predetermined time before and after the fixing process while the recording medium P passes through the nip portion.
Second, when a jam of the recording medium P occurs at any position on the conveyance path of the image forming apparatus main body 1, the occurrence of the jam is detected by a jam detection sensor, and the pressure is reduced based on the detection signal. The rotational drive of the cam member 66 is controlled so as to be in the state.
Third, when the “energy saving mode” is selected on the operation panel (not shown) of the image forming apparatus 1 (a mode in which the fixing temperature is saved lower than that in the fixing step). The rotation of the cam member 66 is controlled so that the pressure is reduced based on the mode selection signal.

In the first embodiment, the cam member 66 is configured such that the pressure roller 30 and the fixing roller are driven by the pressure applied by the pressure roller 30 and the fixing roller 20 when the driving units 90, 91, and 97 are not operating. And 20 so as to be in a reduced pressure state. Specifically, the top portion of the cam member 66 (the peripheral surface portion that engages with the pressure lever 61 in a pressurized state) is not flat but formed relatively sharp. As a result, when the drive motor 90 is not energized, the pressure lever 61 loses its balance without being held on the top of the cam member 66, and the pressure applied between the pressure roller 30 and the fixing roller 20 It moves in the direction in which the pressure is reduced (the movement in the right direction in FIG. 8). That is, in a default state where the drive motor 90 is not energized, the pressure lever 61 rotates so that the pressure roller 30 and the fixing roller 20 are in a reduced pressure state.
With such a configuration, when the main switch of the image forming apparatus 1 is disconnected (off), or when urging members 62 and 63 described later are assembled to the fixing device 19, the pressure roller 30 and the fixing roller 20. Are maintained in a reduced pressure state.

Here, in the first embodiment, the urging members 62 and 63 are moved by the pressure lever 61 while the pressure roller 30 and the fixing roller 20 are maintained in the pressure-reduced state by the pressure-reducing means 64, 66, 90, 91 and 97. The urging members 62 and 63 are configured to be assembled to the fixing device 19 so as to urge them.
Specifically, referring to FIGS. 9 and 10, in the support shaft 62 a of the release lever 62 (second lever member), the distance between the force point shaft 61 b and the hook shaft 67 is variable in conjunction with the rotation of the release lever 62. It is arranged at the position to do. That is, the position of the support shaft 62a is determined such that when the release lever 62 is rotated about the support shaft 62a, the spring length of the tension spring 63 changes depending on the position of the release lever 62 in the rotation direction. It has been.
Then, with the pressure roller 30 and the fixing roller 20 maintained in a pressure-reduced state by the pressure-reducing means 64, 66, 90, 91, 97, the release lever 62 is rotated around the support shaft 62a, and the tension spring 63 is used. The urging members 62 and 63 are assembled to the fixing device 19 so as to urge the pressure lever 61 by the spring force.

A specific assembling procedure of the urging members 62 and 63 is as follows.
First, a pressure lever 61, a slide bearing 64, a cam member 66 (pressure reducing means), and the like are assembled to the side plate 60 on which the fixing roller 20 and the pressure roller 30 are assembled. Then, after the release lever 62 and the hook shaft 67 are assembled to the side plate 60, the hooks of the tension spring 63 are connected to the force point shaft 61b and the hook shaft 67, respectively. At this time, the tension spring 63 is assembled when the release lever 62 is in the position (A) of FIG. 9 (the position where the distance between the force point shaft 61b and the hook shaft 67 is minimum). Therefore, the tension spring 63 is assembled to the fixing device 19 in a state where the spring length is almost free. Therefore, the tension spring 63 can be easily assembled without applying almost any force to the tension spring 63.
After the installation of the tension spring 63 is completed, when the release lever 62 is manually rotated in the direction of the arrow in FIG. ), The position of the release lever 62 is determined at the position (C) in FIG. In this state, the pressure lever 61 is biased by the spring force of the tension spring 63.

Specifically, the tension spring 63 draws a locus as shown in FIG. 10 as the release lever 62 rotates. That is, the spring length of the tension spring 63 is a free length when the tension spring 63 is in the position (A) in FIG. 10 (corresponding to the position (A) in FIG. 9). (B) It is the longest when it is in the position (the position where the force point shaft 61b, the support shaft 62a, and the hook shaft 67 are arranged in a straight line), and the tension spring 63 is in the position (C) in FIG. C) corresponds to the position), and is slightly shorter than the longest length. Accordingly, the spring force of the tension spring 63 increases in the order of (A) position, (C) position, and (B) position.
As described above, the position where the release lever 62 is abutted (the position (C)) exceeds the position (B) where the spring force of the tension spring 63 is maximized. It is possible to suppress a problem that the release lever 62 naturally falls to the position (A) even though 62 is not operated. That is, in order to move the release lever 62 in the (C) position to the (A) position, a force sufficient to change the tension spring 63 from the spring length in the (C) position to the longest length is required. . Note that the force required at this time is a sufficiently small force for the operator who operates the release lever 62.

As described above, when the release lever 62 is rotated from the (A) position to the (C) position, the tension spring 63 becomes longer from the free length. The release lever 62 is operated with a force that resists the spring force that increases as the valve 62 rotates. However, since the pressure roller 30 and the fixing roller 20 are in a pressure-reduced state by the pressure-reducing means 64, 66, 90, 91, 97 at this time, the spring force that increases as the release lever 62 rotates is so large. (It is much smaller than the spring force in the pressurized state in FIG. 7), and the operator can operate the release lever 62 with a relatively small force.
The procedure for removing the urging members 62 and 63 from the fixing device 19 is the reverse of the procedure for assembling described above. At that time, the release lever 62 is rotated in the clockwise direction in FIG. 9 with a relatively small force, and the tension spring 63 is also taken out from the force point shaft 61b and the hook shaft 67 with a relatively small force. Become.

The operation of the first embodiment when the urging members 62 and 63 are assembled to the fixing device 19 is as follows when viewed from the decompression means 64 and 66 side.
That is, in the first embodiment, the decompression means 64, 66 are applied before and after the release lever 62 is rotated about the support shaft 62a and the pressure lever 61 is urged by the spring force of the tension spring 63. The pressure roller 30 and the fixing roller 20 are changed from the first reduced pressure state to the second reduced pressure state. Specifically, the pressure roller 30 and the fixing roller 20 are in a depressurized state both when the release lever 62 is in the (A) position and in the (C) position, but when the release lever 62 is in the (A) position. The degree of decompression in the (first decompression state) is greater than the degree of decompression when the release lever 62 is in the (C) position (second decompression state). That is, the pressure (pressure contact force) between the pressure roller 30 and the fixing roller 20 when the release lever 62 is in the (A) position is the same as the pressure roller 30 and the fixing roller when the release lever 62 is in the (C) position. The pressure (pressure contact force) with 20 is smaller.

  As described above, in the first embodiment, the fulcrum shaft 61a (fulcrum portion) configured to be movable is moved to depressurize the pressure roller 30 (pressure member) and the fixing roller 20 (fixing member). The release lever 62 and the tension spring 63 (biasing member) are assembled to the fixing device 19 so as to bias the pressure lever 61 (lever member) while maintaining the state. Thereby, workability at the time of assembling the release lever 62 and the tension spring 63 for urging the pressure lever 61 can be improved.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 11 is a schematic diagram showing the vicinity of the fixing device of the image forming apparatus according to the second embodiment. The fixing device according to the second embodiment is different from that according to the first embodiment in that the pressure reducing state and the pressing state are switched in conjunction with the opening / closing operation of the cover 100 of the image forming apparatus main body 1.

  Similarly to the first embodiment, the fixing device 19 according to the second embodiment also includes a fixing roller 20, a pressure roller 30, an induction heating unit, and the like. Further, the fixing device 25 includes a pressure lever 61 (lever member), a release lever (second lever member), a compression spring 63, a slide bearing 64 (regulating member), and the like as in the first embodiment. is set up.

Here, the fixing device 19 in the second embodiment is installed on the cover 100 of the apparatus main body 1 instead of the cam member 66 in the first embodiment as an engaging member that engages with the pressure lever 61. The protrusion 100b is used.
Specifically, when the cover 100 of the image forming apparatus main body 1 is closed, the protrusion 100b of the cover 100 is engaged with the pressure lever 61, and the pressure roller 30 and the fixing roller 20 are in a pressurized state. (The state is shown in FIG. 11). At this time, the fulcrum shaft 61a of the pressure lever 61 moves to the left in FIG.
On the other hand, when the cover 100 of the image forming apparatus main body 1 is opened around the hinge 100a, the protrusion 100b of the cover 100 releases the engagement with the pressure lever 61, and the pressure roller 30 The pressure of the fixing roller 20 is reduced. That is, the pressure lever 61 moves in a direction in which the holding force by the protrusion 100b is removed and the pressure is reduced by the pressure between the pressure roller 30 and the fixing roller 20 (FIG. 11). Is moving to the right.) At this time, the fulcrum shaft 61 a of the pressure lever 61 also moves to the right in FIG. 11 along the long hole of the slide bearing 64.

  As described above, in the second embodiment, the protrusion 100b of the cover 100 and the slide bearing 64 function as decompression means. Also in the second embodiment, the urging members 62 and 63 urge the pressure lever 61 while the pressure roller 30 and the fixing roller 20 are maintained in the pressure-reduced state by the pressure-reducing means 64 and 100b. The urging members 62 and 63 are assembled to the fixing device 19.

  As described above, also in the second embodiment, as in the first embodiment, the fulcrum shaft 61a (fulcrum portion) configured to be movable is moved to fix the pressure roller 30 (pressure member) to the fixing roller. The release lever 62 and the tension spring 63 (biasing member) are assembled to the fixing device 19 so as to bias the pressure lever 61 (lever member) while maintaining the roller 20 (fixing member) in a reduced pressure state. Thereby, workability at the time of assembling the release lever 62 and the tension spring 63 for urging the pressure lever 61 can be improved.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 12 is a schematic diagram showing the vicinity of the fixing device of the image forming apparatus according to the third embodiment. The fixing device according to the third embodiment is different from that according to the first embodiment in that the pressure reduction state and the pressure state are switched in conjunction with the attachment / detachment operation with respect to the image forming apparatus main body 1.

  The fixing device 19 according to the third embodiment is also composed of a fixing roller 20, a pressure roller 30, an induction heating unit, and the like, as in the above embodiments. Further, the fixing device 25 includes a pressure lever 61 (lever member), a release lever (second lever member), a compression spring 63, a slide bearing 64 (regulating member), and the like as in the first embodiment. is set up. The fixing device 19 according to the third embodiment is configured such that the pressure lever 61 engages with the fixing roller 20 instead of the pressure roller 30.

Here, in the fixing device 19 according to the third embodiment, as an engaging member that engages with the pressure lever 61, instead of the cam member 66 according to the first embodiment, the protrusion 110 installed in the apparatus main body 1. Is used.
Specifically, when the fixing device 19 is mounted on the image forming apparatus main body 1, the protrusion 110 of the apparatus main body 1 is engaged with the pressure lever 61, and the pressure roller 30 and the fixing roller 20 are in a pressurized state. (The state is as shown in FIG. 12). At this time, the fulcrum shaft 61a of the pressure lever 61 moves to the right in FIG.
On the other hand, when the cover 100 is opened and the fixing device 19 is taken out from the image forming apparatus main body 1, the protrusion 110 of the apparatus main body 1 releases the engagement with the pressure lever 61, and the pressure roller 30 and the fixing roller 20 are decompressed. That is, the pressure lever 61 moves in a direction in which the holding force by the protrusion 110 is removed and the pressure is reduced by the pressure between the pressure roller 30 and the fixing roller 20 (FIG. 12). Is the leftward movement of At this time, the fulcrum shaft 61 a of the pressure lever 61 also moves in the left direction in FIG. 12 along the long hole of the slide bearing 64.

  As described above, in the third embodiment, the protrusion 110 and the slide bearing 64 of the apparatus main body 1 function as a pressure reducing unit that moves the pressure lever 61 to a position away from the fixing roller 20. Also in the third embodiment, the urging members 62 and 63 urge the pressure lever 61 while the pressure roller 30 and the fixing roller 20 are maintained in the pressure-reduced state by the pressure-reducing means 64 and 110. The urging members 62 and 63 are assembled to the fixing device 19.

  As described above, also in the third embodiment, the fulcrum shaft 61a (fulcrum portion) configured to be movable is moved and fixed to the pressure roller 30 (pressure member) in the same manner as each of the above embodiments. The release lever 62 and the tension spring 63 (biasing member) are assembled to the fixing device 19 so as to bias the pressure lever 61 (lever member) while maintaining the roller 20 (fixing member) in a reduced pressure state. Thereby, workability at the time of assembling the release lever 62 and the tension spring 63 for urging the pressure lever 61 can be improved.

In each of the above embodiments, the present invention is applied to the electromagnetic induction heating type fixing device 19 using the exciting coil 26 as the heating means. However, an electronic device such as a fixing device using a heater as the heating means is used. Naturally, the present invention can be applied to all fixing devices used in photographic image forming apparatuses.
In each of the above embodiments, the present invention is applied to the fixing device using the fixing roller 20 as the fixing member and the pressure roller 30 as the pressure member. However, a fixing belt or a fixing film is used as the fixing member. The present invention can also be applied to the fixing device used and a fixing device using a pressure belt or a pressure pad as a pressure member.
In these cases, the same effects as those in the above embodiments can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view illustrating a fixing device. FIG. 3 is a perspective view showing a main part of the fixing device. It is a side view showing a pressure mechanism of the fixing device. FIG. 4 is a perspective view showing a pressure mechanism of the fixing device. It is a top view which shows the vicinity of the hook part to which the tension | pulling spring was connected. FIG. 6 is a side view showing a pressure state of the fixing device. FIG. 6 is a side view showing a reduced pressure state of the fixing device. FIG. 6 is a side view illustrating a state in which an urging member is assembled to the fixing device. FIG. 10 is a schematic view showing the operation of the tension spring at the time of FIG. 9. FIG. 6 is a schematic diagram showing the vicinity of a fixing device of an image forming apparatus according to Embodiment 2 of the present invention. FIG. 10 is a schematic diagram illustrating the vicinity of a fixing device of an image forming apparatus according to Embodiment 3 of the present invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
19 fixing device,
20 fixing roller (fixing member),
25 induction heating unit,
30 pressure roller (pressure member),
61 Pressure lever (lever member),
61a fulcrum shaft (fulcrum part), 61b force point axis (force point part),
61c Stopper shaft,
62 Release lever (second lever member),
62a spindle,
63 Tension spring (biasing member),
64 slide bearing (regulating member),
66 cam member (engaging member),
67 Hook shaft (hook part)
90 drive motor (drive unit), 91 gear train (drive unit),
100 cover, 100b protrusion (engagement member),
110 Projection (engagement member).

Claims (9)

A fixing member that heats and melts the toner image and fixes the toner image on the recording medium;
A pressure member that forms a nip portion to which a recording medium is conveyed by being pressed by the fixing member;
It is installed so as to be rotatable around a fulcrum part, and is urged by an urging member installed at a force point part, so that the pressure member or the A lever member that engages the fixing member to bring the pressure member and the fixing member into a pressurized state;
Pressure reducing means for moving the fulcrum portion of the lever member to a position away from the pressure member or the fixing member to bring the pressure member and the fixing member into a reduced pressure state;
With
The fixing device, wherein the urging member is assembled to the apparatus so as to urge the lever member while the pressure member and the fixing member are maintained in a reduced pressure state by the pressure reducing means. The biasing member is
A tension spring having one end connected to the force point of the lever member;
A second lever member having a hook portion to which the other end of the tension spring is connected and configured to be rotatable about a support shaft;
Comprising
The support shaft of the second lever member is disposed at a position where the distance between the force point portion and the hook portion is variable in conjunction with the rotation of the second lever member,
The urging member rotates the second lever member about the support shaft while maintaining the pressure member and the fixing member in a pressure-reduced state by the pressure-reducing means, and by the spring force of the tension spring. The fixing device according to claim 1, wherein the fixing device is assembled to the device so as to urge the lever member.   The pressure reducing means rotates the second lever member about the support shaft and urges the pressure member and the fixing member before and after biasing the lever member by a spring force of the tension spring. The fixing device according to claim 2, wherein the fixing device is variable from the reduced pressure state to the second reduced pressure state. The decompression means includes
A regulating member that regulates the direction in which the fulcrum portion of the lever member moves;
An engaging member that engages with the lever member;
The fixing device according to claim 1, wherein the fixing device is provided. The engaging member is a cam member,
5. The cam member according to claim 4, wherein the cam member is rotationally driven by a drive unit and maintains a posture in a rotation direction to switch the pressure member and the fixing member from a reduced pressure state to a pressurized state. Fixing device.   The cam member is rotated so that the pressure member and the fixing member are brought into a reduced pressure state by the pressure of the pressure member and the fixing member when the driving unit is not operating. The fixing device according to claim 5. The engaging member is a protrusion provided on the cover of the image forming apparatus main body,
The protrusion engages with the lever member when the cover of the image forming apparatus main body is closed to place the pressure member and the fixing member in a pressurized state, so that the protrusion of the image forming apparatus main body is The fixing device according to claim 4, wherein when the cover is opened, the engagement with the lever member is released, and the pressure member and the fixing member are brought into a reduced pressure state. The engaging member is a protrusion provided on the image forming apparatus main body,
The protrusion engages with the lever member when the apparatus is mounted on the image forming apparatus main body to place the pressure member and the fixing member in a pressurized state, and the apparatus is moved from the image forming apparatus main body to the apparatus. 5. The fixing device according to claim 4, wherein when being taken out, the engagement with the lever member is released to put the pressure member and the fixing member in a reduced pressure state.   An image forming apparatus comprising the fixing device according to claim 1.

Images